When designing a fiber optic illumination system, the system designer is inevitably faced with situations where the optical fiber has to make a sharp bend around a corner. This is particularly common in aircraft and aerospace applications where an optical fiber must be routed around bulkheads, door jams, etc. This problem often cannot be solved by using just the bend radius of the optical fiber or optical fiber bundle. One solution, however, is to use a prism or mirror to reflect light exiting from one optical fiber into a separate optical fiber, to thereby channel the light around a corner or sharp bend. However, prisms and mirrors suffer from inherent inefficiencies due to beam expansion through the prism or mirror. Furthermore, with regard to the mirror, this component will produce a reflectivity loss due to the optical coating that is typically employed thereon.
Total Internal Reflection (TIR) is a well known phenomenon that is the most efficient way to preserve the most light directed toward a target surface. It has been found that an ellipsoidal, solid, transparent image will TIR any light from one focus of the ellipsoidal shape to the other focus, where the light reflects off the curved surface of the ellipsoid between its two focal planes. The ability to use TIR in reflecting light between a first optical cable and a second optical cable would be highly desirable because TIR is an extremely efficient light reflection mechanism. TIR is known to be capable of reflecting about 99.9% of the light signal from a source (i.e., bulb, fiber feed light guide, etc.) at one focus to an accepting output device (i.e., optical fiber bundle, light guide, etc.) at the other focus.
Accordingly, it would be highly desirable to provide an optical coupling device that incorporates TIR for channeling light around a corner or bend between two optical fibers.
It would also be desirable to provide such a coupling device as described immediately above that does not include a large number of independent component parts, that is relatively light in weight and compact, and which is therefore ideally suited for aircraft and aerospace applications.